Questions: A 9 W lamp produces 108 lumens. Calculate the luminous efficacy of the lamp.

Transcript text: A 9 W lamp produces 108 lumens. Calculate the luminous efficacy of the lamp.

Solution

Step 1: Understand the Given Data

We are given:

Step 2: Define Luminous Efficacy

Luminous efficacy (\( \eta \)) is defined as the ratio of luminous flux (\( \Phi \)) to power (\( P \)).

\[ \eta = \frac{\Phi}{P} \]

Step 3: Calculate Luminous Efficacy

Substitute the given values into the formula:

\[ \eta = \frac{108 \, \text{lumens}}{9 \, \text{W}} = 12 \, \text{lumens/W} \]

\[ \boxed{\eta = 12 \, \text{lumens/W}} \]

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